The present invention relates to apparatus for continuously dyeing a web of fabric, particularly pile fabric such as carpets and moquettes. It is a self-contained type which can perform all the steps including preheating, spray dyeing, cooling, rinsing, etc.
For the dyeing of a web of fabric, there are the wince dyeing process and the continuous dyeing process. The latter was developed as a substitute for the former and has an increased productivity.
As described e.g. in the "Fabric Manual" issued by Maruzen Co., Ltd. on May 30, 1970, on pages 956-960, the conventional apparatus for continuous dyeing has separate units merely coupled with one another. These units each serve for the giving of a dye, drying, giving of chemicals, steaming, airing, reduction, dry heating, after-treatment, and rinsing. As a method for giving a dye, it is known to spray heated dye to a preheated fabric by means of spray nozzles (e.g. from Japanese patent publications Nos. 52-48222, 53-4155, 54-4434 and 56-47303 and Japanese patent laid-open publications Nos. 55-152855, 56-364 and 56-140158).
With such a conventional apparatus for continuous dyeing, heat consumption is extremely large. In order to decrease the heat consumption, it is required to minimize the volume of dye supplied to the fabric. For this purpose, various methods are known e.g. to squeeze the fabric with a mangle or to coat the fabric with dye by means of rolls. However, such methods are not satisfactory because the wider and the thicker the fabric is, the more difficult it is to squeeze or coat uniformly.
The spray method using spray nozzles is a more effective method because the adjustment of the dye pressure is easy. However, spraying a dye against the fabric on a flat conveyor (as disclosed in the abovesaid Japanese patent publications) or against a concave surface of the fabric can cause listing, frosting or ending even in a wet heat condition. The wider and the thicker the fabric is, the more marked this tendency is.
Other problems to be solved include difference in color between lots, difficulty in dyeing fine gauge fabric, and poor contrast in dyeing fabric having yarns with different dye-reactivity. Savings in dyeing time and of dye, dye-assist and water are other requirements to be met.
It is known that treating polyamide fabric with a copper salt increases light-fastness. However, treating the dyed fabric with a copper salt can smudge it with green peculiar to a copper salt. Therefore, it is usual to put a copper salt in the dye to add copper at the same time with dyeing. This also can give a bad effect on the size used and decrease the viscosity in continuous dyeing.
It is also known to after-treat the dyed fabric with an oxidation inhibitor (to increase the heat resistance) or with an ultraviolet absorbing agent (to increase the light resistance). Because of their low affinity to polyamide fabric, such chemicals have to be used in high concentration (e.g. 30-40 g/l) to obtain an expected effect. This results in a considerable loss in the subsequent drying step.
In a continuous dyeing of wool fabric, the pick-up of dye is smaller than in the wince dyeing, and steaming for heat treatment is performed only in a short time. So the felting, which often occurs in the wince dyeing due to the intertwining of scales on the surface of wool fabric, is less likely to happen. But, shorter time for heat treatment decreases the fastness to dyeing, laundering and rubbing. This tendency is marked for dark colors.
Because of its high resistance to light and heat, polyester fabric has an active demand for various goods. But, thick web of fabric is not easy to dye. Thus, it is usually yarn-dyed by the high-pressure batch process. The continuous dyeing process has not been used for this fabric because sealing at the inlet and outlet of an apparatus poses a problem. Also, as in the invention disclosed in the Japanese patent publication No. 52-25469, as the dye at normal temperature is heated in a hot steamer, water in the dye liquid will be evaporated and the fabric is gradually dried. In this step, the migration of a disperse dye used is inevitable. Disperse dyes are generally highly sensitive to heat and it is difficult to keep the whole part of thick fabric at a uniform temperature, and distribution of overheated steam is not uniform. So it is difficult to prevent the migration of disperse dye. Therefore, treatment in a hot steamer requires the use of a size.
An object of the present invention is to provide an apparatus for dyeing a web of fabric continuously, which obviates the abovesaid shortcomings.